Page 355 - Elements of Chemical Reaction Engineering Ebook

326 Multiple Reactions Chap. 6

Additional information:
Feed: 22.5 SCFIs of pure A
Reaction conditions: 46OoF, 3 atm pressure
Volumetric flow rate: 15 ft3/s at reaction conditions
Concentration of A in feed: 4.47 X Ib mol/ft3
P6-11B The following liquid-phase reactions were carried out in a CSTR at 325 K.

3A + B+C -ri~ = ~~ACA k,, = 0.7min-'
4D+3C - k,D = 0.3 mol2 - min
dm6
2C+A L_) 3D
k,, = 0.2 -
dm3
3E
mol 3 min
The concentrations measured inside the reactor were CA = 0.10, CB = 0.93,
C, = 0.51, and CD = 0.049 all in mol/dm3.
(a) What are rlA, r,,, and r3A? (rlA = -0.07 mol/dm3.min)
Sketch the trends or (b) what are ri~, ~2.13, and r3~?
results you expect (c) What are'rlc, rZc, and r3c? (Ilc = 0.023 mol/dm3-min)
before working out (d) What are rlD, rZD, and r3D?
the details of the (e) What are rlE, r2E. and r3E?
problem. (f) What are the net rates of formation of A, B, C, D, and E?
(g) The entering volumetric flow rate is 100 dm3/min and the entering concentra-
tion of A is 3 M. What is the CSTR reactor volume? (Am.: 4OOO dm3.)
(h) Wnte a Polymath program to calculate the exit concentrations when the vol-
ume is given as 6OOO dm3.)
P6-12 Calculating the space-time for parallel reactions. m-Xylene is reacted over a
ZSM-5 zeolite catalyst. The following parallel elementary reactions were
found to occur [Znd Eng. Chem Res., 27, 942 (1988)l:

m-xylene kl + benzene + methane
>
m-xy lene ' p-xylene
(a) Calculate the space-time to achieve 90% conversion of m-xylene in a
packed-bed reactor. Plot the overall selectivity and yields as a function of
z. The specific reaction rates are k, = 0.22 s-l and k2 = 0.71 s-' at
673°C. A mixture of 75% m-xylene and 25% inerts is fed to a tubular
reactor at volumetric flow rate of 2000 dm3/min and a total concentration
of 0.05 mol/dm3. As a first approximation, neglect any other reactions
such as the reverse reactions and isomerization to o-xylene.
(b) Suppose that E, = 20,000 caVmol and E2 = 10,000 cdmol, what tem-
perature would you recommend to maximize the formation of p-xylene
in a CSTR with a space-time of 0.5 s?
P6-13, The following liquid phase reactions are carried out isothermally in a 50 dm3
PFR:
B+2C - rpI=kpICBC:
A+2B ___) C+D
rD,=k,,CACi
2D+3A ___) C+E rEz=kE2CAcD
D+F